load and save layer visibility in openraster

BUG:277200

krita/ui/openrastertk/kis_open_raster_stack_load_visitor.cpp

@@ -105,6 +105,11 @@ void KisOpenRasterStackLoadVisitor::loadLayerInfo(const QDomElement& elem, KisLa
     layer->setName(elem.attribute("name"));
     layer->setX(elem.attribute("x").toInt());
     layer->setY(elem.attribute("y").toInt());
+    if(elem.attribute("visibility") == "hidden") {
+        layer->setVisible(false);
+    } else {
+        layer->setVisible(true);
+    }
 
     QString compop = elem.attribute("composite-op");
     if (compop.startsWith("svg:")) {

krita/ui/openrastertk/kis_open_raster_stack_save_visitor.cpp

@@ -54,6 +54,7 @@ void KisOpenRasterStackSaveVisitor::saveLayerInfo(QDomElement& elt, KisLayer* la
 {
     elt.setAttribute("name", layer->name());
     elt.setAttribute("opacity", layer->opacity() / 255.0);
+    elt.setAttribute("visibility", layer->visible() ? "visible" : "hidden");
 
     QString compop = layer->compositeOpId();
     if (layer->compositeOpId() == COMPOSITE_CLEAR) compop = "svg:clear";